Flowing-water remediation simulation experiments of lead-contaminated soil using UCB technology.

The flowing-water remediation of contaminated soil was investigated. Urease combined with biochar (UCB) technology was used to handle the Pb²⁺-contaminated sand column. The results showed that with the continuous increase of pore volume, the concentration of Pb²⁺ in the leachate undergoes three stages: slow growth, rapid growth, and steady state. With increasing seepage velocity, the concentration of Pb²⁺ in leachate increased slightly. The residual amount of each section of the sand column gradually decreased with increasing migration distance. The comparative results indicated that the UCB technology had a good solidification effect on Pb²⁺. This was due to urease-induced CaCO₃ precipitation, cementation, and adsorption of Pb²⁺. Biochar provided more nucleation sites for urease, and some Pb²⁺ was adsorbed on its surface or diffused into the pores of biochar, or ions exchanged with functional groups on the surface of biochar, which effectively stabilized the free Pb²⁺.